Methanol oxidation catalyst

Abstract

The present invention provides a catalyst composition comprising: i) a catalytic material comprising iron molybdate (Fe2 (MoO4) 3) and molybdenum trioxide (MoO3); and ii) a metal oxide A, wherein the metal oxide A is an alkaline earth metal oxide, or a zirconium oxide, or a combination of a zirconium oxide and a cerium oxide.

Description

Technical Field

[0001] The present invention relates to a catalyst composition for the oxidation of methanol to produce formaldehyde, and in particular to a catalyst composition that reduces the production of methyl formate, an undesirable by-product. Background Art

[0002] Processes for producing formaldehyde by oxidizing methanol over a catalyst have been known for many years. One well-known process involves oxidizing methanol over a mixed oxide catalyst, typically containing iron and molybdenum oxides: CH3OH + 0.5O2 → CH2O + H2O. Plants operating this process typically operate at a reactor inlet pressure of about 1 barg or less. Further increases in pressure can cause problems due to a loss of catalyst selectivity. This results in an increased formation of unwanted by-products such as carbon monoxide, dimethyl ether, and methyl formate. Consequently, the utilization of the added raw materials is reduced compared to the case where no by-products are formed, leading to higher operating costs. Given that methanol contributes >90% to the total operating costs, minimizing these losses is highly desirable.

[0003] Methyl formate can be formed according to the following reaction:

[0004] 2CH3OH+O2→HCOOCH3+2H2O

[0005] 2HCHO→HCOOCH3

[0006] CH3OH+CH2O+1 / 2O2→HCOOCH3+H2O

[0007]

[0008] Reducing methyl formate is desirable because it also reduces formaldehyde yields and operator profitability, and results in the production of formic acid according to the equilibrium reaction described above. For example, for manufacturers of adhesives and urea-formaldehyde, formic acid is problematic and requires the addition of buffers to formalin solutions.

[0009] The present invention seeks to overcome one or more of the above-mentioned disadvantages of the prior art.In particular, the present invention seeks to reduce methyl formate losses in a process for producing formaldehyde. Summary of the Invention

[0010] Therefore, the present invention provides a catalyst composition comprising:

[0011] i) a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and

[0012] ii) Metal oxide A, wherein the metal oxide A is an alkaline earth metal oxide, or zirconium oxide, or a combination of zirconium oxide and cerium oxide.

[0013] In particular, the present invention provides a catalyst composition according to the present invention, the catalyst composition comprising:

[0014] i) particles of said catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and

[0015] ii) metal oxide A;

[0016] wherein the catalyst composition comprises a physical blend of the catalytic material and the metal oxide A, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and

[0017] wherein at least some of the metal oxide A forms a coating around the particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

[0018] Such catalyst compositions advantageously promote the oxidation of methanol to formaldehyde while reducing the selectivity to methyl formate without a significant decrease in methanol conversion.

[0019] The present invention also provides pellets comprising the catalyst composition of the present invention. Such pellets maintain hardness at relatively low densities, i.e., they exhibit an improved hardness-to-density ratio. Lower-density tablets are more active and selective in methanol oxidation. For example, formaldehyde overoxidation is reduced, resulting in less carbon monoxide formation. However, tablets with relatively low densities are generally less durable. The pellets of the present invention address this problem.

[0020] The present invention also provides a method for preparing the catalyst composition according to the present invention, the method comprising the following steps:

[0021] i) calcining metal oxide A to provide calcined metal oxide A;

[0022] ii) mixing the calcined metal oxide A with a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3);

[0023] iii) calcining the mixture to provide the catalyst composition.

[0024] The present invention also provides a method for preparing the catalyst composition of the present invention, the method comprising the following steps:

[0025] i) calcining metal oxide A to provide calcined metal oxide A;

[0026] ii) calcining a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3);

[0027] ii) mixing the calcined metal oxide A with a calcined catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

[0028] The present invention also provides a process for producing formaldehyde from methanol, comprising the steps of: feeding a feed stream comprising methanol and an oxygen-containing gas to a reactor; and reacting the methanol in gas phase with the oxygen-containing gas in the reactor in the presence of the catalyst composition or tablet according to the present invention.

[0029] The present invention also provides the use of the catalyst composition of the invention for reducing methyl formate losses in a process for producing formaldehyde from methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a graph showing methyl formate selectivity versus methanol conversion for a comparative catalyst and a catalyst composition according to the present invention.

[0031] Figure 2 is a graph showing methyl formate selectivity versus methanol conversion for a comparative catalyst and additional catalyst compositions according to the present invention.

[0032] Figure 3 is a graph showing methyl formate selectivity versus methanol conversion for a comparative catalyst and additional catalyst compositions according to the present invention.

[0033] Figure 4 is a graph showing methyl formate selectivity versus methanol conversion for a comparative catalyst and additional catalyst compositions according to the present invention.

[0034] Figure 5 is a graph showing density versus hardness for pellets containing a catalyst composition according to the present invention.

[0035] Figure 6 is a TEM image of a catalyst composition according to the present invention.

[0036] Figure 7 is a collection of EDS images of catalyst compositions according to the present invention. DETAILED DESCRIPTION

[0037] The catalyst composition of the present invention comprises a catalytic material which is a mixture of iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3), with a Mo:Fe ratio generally between 2 and 3. Suitable catalytic materials have a molar mass of 2m 2 / g to 20m 2 / g range and including 2m 2 / g and 20m 2 / g (e.g. 3m 2 / g to 10m 2 / g) of surface area. The catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) may optionally contain copper, for example as described in WO2022 / 079434, and / or oxides of other metals such as vanadium, aluminum, silicon, calcium, cobalt, chromium, magnesium, manganese, nickel, zinc, silver, and titanium. As will be appreciated by the skilled artisan, such additional components will be present in small amounts, such as no more than about 1.0% by weight, and typically no more than 0.5% by weight.

[0038] The catalyst composition of the present invention further comprises a metal oxide A, wherein the metal oxide A is an alkaline earth metal oxide, or a zirconium oxide, or a combination of a zirconium oxide and a cerium oxide. In one aspect, the metal oxide A is an alkaline earth metal oxide. The preferred alkaline earth metal oxide is magnesium oxide. In one aspect, the metal oxide A is a zirconium oxide. In another aspect, the metal oxide A is a combination of a zirconium oxide and a cerium oxide, for example in a weight ratio ranging from 5:1 to 1:5, including 5:1 and 1:5, and typically in a weight ratio of about 1:1.

[0039] Typically, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is in the form of particles, suitably produced by agglomeration of particles of the catalytic material. Suitably, the catalyst composition is a physical blend of the catalytic material and metal oxide A, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3). For example, discrete solid forms of the catalytic material and metal oxide A are present in the catalyst composition. Suitably, at least some of the metal oxide A forms a coating around particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3). For example, the discrete solid forms of metal oxide A are typically uniformly distributed over substantially all of the surface of the catalytic material particles and are bound or fixed to the particles by physical or chemical bonds. In other words, the catalyst composition comprises particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) dry-coated with metal oxide A, the particles suitably having a uniform coating. Typically, at least about 50 weight percent of the metal oxide A forms a coating around particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

[0040] Typically, metal oxide A can be present in an amount of no more than about 15 wt % based on the total weight of the catalyst composition, preferably no more than about 5 wt % based on the total weight of the catalyst composition, more preferably no more than about 3 wt % based on the total weight of the catalyst composition, and even more preferably no more than about 2 wt % based on the total weight of the catalyst composition. Metal oxide A is typically present in an amount of at least about 0.1 wt % based on the total weight of the catalyst composition.

[0041] The catalyst composition may also comprise an alkali metal, suitably sodium. Preferably, the metal oxide A is impregnated with an alkali metal. The alkali metal is suitably present in an amount of no more than about 5 wt % based on the weight of the metal oxide A, preferably no more than about 1 wt % based on the weight of the metal oxide A, and more preferably no more than about 0.5 wt % based on the weight of the metal oxide A. The alkali metal is typically present in an amount of at least about 0.1 wt % based on the total weight of the catalyst composition.

[0042] To prepare the catalyst composition, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is typically first sieved to obtain a particle size in the range of about 200 μm to about 400 μm, including about 200 μm and about 400 μm, as measured by sieving. In one aspect, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is then calcined, typically at a temperature in the range of about 400°C to about 550°C, including about 400°C and about 550°C, before being mixed with metal oxide A. In this regard, there is typically no calcination step following the step of mixing the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) with metal oxide A. In an alternative aspect, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is not calcined before being mixed with metal oxide A. In this alternative aspect, it is desired to calcine the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) after mixing it with metal oxide A. Such calcination can be carried out at a temperature ranging from about 400°C to about 550°C, inclusive, and typically for a period of less than about 120 hours. In the case of all calcination steps discussed herein, the calcination time is not particularly limited, and the calcination can be carried out for as long as is necessary for the desired surface area of ​​the material. The total time will depend on factors such as the furnace used, flow conditions, and heat transfer, and the skilled person using common knowledge can determine the required time. As demonstrated in the Examples section, both synthetic methods provide catalyst compositions, which generally comprise a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) dry-coated with metal oxide A, and achieve the benefits of the present invention. In either aspect, metal oxide A is calcined prior to mixing with the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3). Such calcination can be carried out at a temperature ranging from about 300°C to about 1200°C, including about 300°C and about 1200°C, typically for a period of less than about 120 hours. The mixing of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) with metal oxide A can be any form of physical mixing, typically a blending of two solid forms, for example, performed manually or using automated means such as resonant acoustic mixing. Suitably, metal oxide A has a particle size measured by sieving that is smaller than the particle size measured by sieving of particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3). As demonstrated in the Examples section, the specific method for blending is not particularly limited, which is a benefit of the catalyst composition. When the catalyst composition comprises an alkali metal, metal oxide A is preferably impregnated with an alkali metal.This is typically achieved by precipitating the alkali metal from a solution (typically an aqueous solution) of a soluble alkali metal salt in the presence of a metal oxide A that has not undergone calcination. This can be accomplished by adding the solution dropwise to the metal oxide A before the heating step (e.g., in the range of about 80°C to about 120°C and including about 80°C and about 120°C). In order to uniformly distribute the alkali metal, the soluble alkali metal salt can be dissolved in enough solvent (typically water) to fill the pores of the metal oxide A without overfilling. Technicians can determine such an amount using common knowledge. The impregnated metal oxide A is then calcined at a temperature in the range of about 300°C to about 1200°C and including about 300°C and about 1200°C, typically for a period of less than about 120 hours. Alkali metal salts are, for example, hydroxide salts and chloride salts.

[0043] The catalyst composition of the present invention can be incorporated into a shaped or extruded catalyst. Therefore, provided herein is a shaped or extruded catalyst comprising a catalyst composition of the present invention. The catalyst composition can be shaped into pellets, preferably annular pellets. Therefore, provided herein is a pellet comprising a catalyst composition of the present invention, preferably annular pellets. The size of such pellets will depend on the specific application. Suitably, the annular pellets have an outer diameter in the range of about 4.5 mm to about 5.5 mm and include an outer diameter of about 4.5 mm and about 5.5 mm. Suitably, the annular pellets have an inner diameter in the range of about 2.0 mm to about 3.7 mm and include an inner diameter of about 2.0 mm and about 3.7 mm. Suitably, the annular pellets have a height in the range of about 2.0 mm to about 5.5 mm and include a height of about 2.0 mm and about 5.5 mm. The pellets can be formed using standard means known to those skilled in the art, and the method can include the use of additives, such as lubricants, i.e. graphite, and pore formers. Typically, these additives will be removed during the subsequent heating step. However, for example, some lubricant may remain in the formed pellets in an amount of less than about 1% by weight. After the step of forming the pellets, a heating step is performed. In a method for preparing a catalyst composition in which there is a step iii) of calcining the mixture to provide the catalyst composition of the present invention, the step of forming the pellets is performed before this step iii), and the calcining step thus provides the required heat. The pellets suitably have a ratio of hardness, generally in the axial direction, to density of greater than 9, typically greater than 10. The ratio of hardness to density is hardness (kP) / density (g / cm 3). The pellets suitably have a hardness in the axial direction of at least about 7 kP, typically at least about 20 kP. The pellets typically have a hardness in the axial direction of at most about 40 kP. The hardness is measured in the axial direction on annular pellets having an outer diameter of 5.0 mm, an inner diameter of 2.75 mm and a height of 2.5 mm by a Sotax MultiTest 50-FT WTDH 800N 100-240 V / 50-60 Hz or any equivalent instrument. The pellets also suitably have a hardness of at most about 2.2 g / cm 3 , usually up to about 2.0g / cm 3 , more typically less than about 1.9 g / cm 2 The pellets typically have a density of at least about 1.5 g / cm 3 The density of the tablet is calculated using the average mass and volume of 10 tablets at ambient temperature and pressure (e.g., 25°C and 1 atm). The size of the volume can be measured, for example, using an optical microscope.

[0044] Typical processes for producing formaldehyde from methanol are known, for example, from WO 96 / 32189 and US 2,504, 402. A well-known process for producing formaldehyde is the Formox process provided by Johnson Matthey, described, for example, in WO 2022 / 079434.

[0045] In a process for producing formaldehyde from methanol, the reactor can be operated at an inlet pressure suitable for the particular process and available plant equipment. The skilled person must select an appropriate reactor pressure based on the equipment and the desired results. A typical process plant for formaldehyde production using a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) can operate at a reactor inlet pressure of about 0 barg. Barg represents gauge pressure, measured in bar, i.e., pressure above atmospheric pressure. Barg can be converted to bar absolute (bara) by adding the local atmospheric pressure in bar. Using the process of the present invention, the reactor inlet pressure can be at least 0.4 barg. A particular benefit of the process of the present invention is that the reactor inlet pressure can be increased without increasing or even while still reducing methyl formate losses. In other words, because the present invention reduces methyl formate losses at the same pressure compared to prior art processes, prior art processes can apply the present invention and increase the pressure and still maintain the same or better methyl formate losses and / or methyl formate losses. Thus, the reactor inlet pressure may preferably be at least about 0.4 barg, more preferably at least about 1.0 barg, still more preferably greater than about 1.5 barg, and even more preferably greater than about 3 barg.The reactor inlet pressure may be up to or above about 10 barg.

[0046] The oxygen-containing gas can be any suitable gas stream. In the reactor, the concentration of oxygen is selected by the process designer according to the technology of expectation. For example, oxygen concentration can be selected so that the mixture of oxygen and organic compound does not explode. In typical formaldehyde production methods, the oxygen-containing gas is air. The oxygen-containing gas can be in the reactor, at the reactor inlet or before the feed stream is fed by the reactor inlet, mixed with other components of methanol and feed stream (such as recycle stream).

[0047] The feed stream may comprise methanol at a concentration of 1% to 20% by volume of the feed stream.The feed stream may comprise methanol at a concentration of 3% to 15% by volume, such as from about 6% to about 12% by volume.

[0048] In a typical process, the reaction product leaving the reactor, which contains some product formaldehyde, is treated to remove a portion of the product formaldehyde from the formaldehyde reactor outlet stream. This produces a formaldehyde product stream (containing the removed formaldehyde product) and a treated stream (containing some formaldehyde as well as other by-products, such as carbon monoxide and typically unreacted methanol, water, and dimethyl ether). Other by-products may also include nitrogen, for example, if the oxygen-containing gas used is air. A portion of the treated stream can be recycled to the reactor. In this case, the feed stream entering the reactor may contain dimethyl ether produced as a by-product in the reactor. It is known that when dimethyl ether is added to the reactor, the amount of dimethyl ether produced in the reaction tends to be less. The feed stream may, for example, contain up to about 0.7% by volume of dimethyl ether. Typically, the feed stream may contain about 0.1 to about 0.6% by volume of dimethyl ether. The conversion of methanol to dimethyl ether is a known problem that affects the productivity of the formaldehyde process, particularly when operating at higher inlet pressures. The presence of water in the feed stream entering the reactor can reduce the amount of dimethyl ether formed. Water can be added as described in WO2016 / 177999. Preferably, sufficient water is added to the feed stream to bring the amount of water in the feed stream to a value in the range of about 3.0% to about 15.0% water by volume, preferably about 3.5% to about 10.0% by volume.

[0049] The reaction temperature of the reaction of the oxygen-containing gas with methanol in the gas phase in the reactor is typically greater than about 250°C, normally between about 250°C and about 400°C. The reactor feed inlet temperature may typically range from about 60°C to about 220°C. The reaction temperature may vary along the length of the reactor bed. The reactor is typically operated so that the temperature is at a maximum at a location between the inlet and outlet portions of the reactor. The reaction temperature in different parts of the reactor may be affected by the composition of the catalyst in the catalyst bed. Mixed catalyst beds may be used, in which the catalyst may be mixed with an inert material or with catalysts of different compositions and activities to provide a desired activity distribution across the catalyst bed. In particular, the catalyst composition of the present invention may be used in only a portion of the reactor. The reactor may contain a catalyst bed, such as in a fixed bed reactor. The reactor will more typically contain multiple parallel catalyst beds, such as in a tubular reactor, in which multiple tubes containing the catalyst beds are each surrounded by a heat transfer fluid. A tubular reactor may typically contain hundreds or thousands of such tubes. Preferably, the downstream third of one or more catalyst beds may contain the catalyst composition of the present invention. The downstream half of one or more catalyst beds may contain the catalyst composition of the present invention. The catalyst composition of the present invention can be used in the downstream portion of one or more catalyst beds, since the majority of the methyl formate is formed there. The catalyst composition of the present invention can be used in the entirety of one or more catalyst beds, or in the upstream portion of one or more catalyst beds. If the activity of the catalyst composition of the present invention differs from the activity of a standard catalyst of the prior art, it may be particularly advantageous to use the catalyst composition of the present invention in only a portion of one or more catalyst beds.

[0050] The reaction temperature can be controlled by a heat transfer system. The reactor temperature can be varied over time. Typical catalysts tend to lose activity over their useful life. To account for this loss of activity, the reactor temperature can be varied.

[0051] Example

[0052] Example 1

[0053] Commercial MgO (Sigma-Aldrich, 325 mesh) was calcined in a static oven at a heating rate of 5°C / min (typically up to 600°C or 1000°C) and maintained at the target temperature for 2 hours. An amorphous methanol oxidation catalyst (Mo-Fe catalyst) comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) as described in Topics in Catalysis, 50, 2008, pp. 145-155 was sieved to a particle size in the range of 250 μm to 355 μm. The Mo-Fe catalyst (14.85 g) was added to a reaction tank, and calcined MgO (0.15 g) was added. This was intended to obtain a final product comprising 99 wt % of the Mo-Fe catalyst and 1 wt % of the MgO. The reaction tank was then subjected to resonant acoustic mixing (RAM) using a LabRAMII instrument at a force of 80 g for 5 minutes. The samples were then calcined at temperatures ranging from 400°C to 500°C to obtain the final catalyst. The following two catalyst compositions were prepared according to this method:

[0054] 1a—It contains 1% by weight of MgO which has been previously calcined at 600°C.

[0055] 1b—It contains 1% by weight of MgO which has been previously calcined at 1000°C.

[0056] Methyl formate selectivity % and methanol conversion % were evaluated for 1a and 1b, as well as a reference methanol oxidation catalyst comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) as described in Topics in Catalysis, 50, 2008, pp. 145-155-C1.

[0057] The evaluations were conducted in a microreactor at 330°C, 0.5 barg, and a total gas flow rate of 400 Nml / min; the concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0 vol%, 1.4 vol%, 0.2 vol%, 0.26 vol%, 4.06 vol%, 10.0 vol%, and 77.08 vol%, respectively. In separate experiments, the weights of the C1 catalyst used in the microreactor were 0.1 g, 0.15 g, 0.2 g, and 0.25 g, which give the values ​​of Figure 1 The increase in conversion is shown in Figure 2. The weight of catalyst compositions 1a and 1b used in the microreactor tests was 0.2 g. Figure 1 It is shown that for 0.2 g of catalyst, the selectivity for methyl formate decreases without a significant decrease in methanol conversion. It can be speculated that this effect will also be seen at higher catalyst loadings and methanol conversions.

[0058] Example 2

[0059] Three series of catalyst compositions were prepared to investigate the effect of different variables on the reduction in methyl formate selectivity. The factors investigated consisted of MgO loading, the effect of adding Na to MgO, and the method of mixing the Mo-Fe catalyst with MgO (with or without added Na).

[0060] Variation of MgO loading on Mo-Fe catalysts and RAM mixing of components

[0061] First, commercial MgO (Sigma-Aldrich, 325 mesh) was calcined to 1000°C using a static oven at a heating rate of 5°C / min and held at the target temperature for 2 hours. The amorphous Mo-Fe catalyst was sieved to a particle size in the range of 250 μm to 355 μm. The final calcined catalyst composition was prepared according to the same method described in Example 1. The following table shows the amount of reactants used for each catalyst composition in this series:

[0062] MgO, weight % MgO(g) Mo-Fe catalyst (g) 2a 2 0.3 14.7 2b 3 0.45 14.55 2c 4 0.6 14.4 2d 5 0.75 14.25

[0063] Table 1

[0064] Variation of Na-impregnated MgO loading on Mo-Fe catalysts and RAM mixing of components

[0065] First, commercial MgO (Sigma-Aldrich, 325 mesh) was calcined to 1000°C at a heating rate of 5°C / min in a static oven and maintained at the target temperature for 2 hours. Subsequently, NaCl was dissolved in enough desalted water to fill the pores of the MgO without overfilling to uniformly distribute the NaCl. The amount of solution required for each gram of calcined MgO was 0.60g / ml. In a glass beaker, 9.98g of calcined MgO was weighed. In a separate beaker, 0.05g of NaCl was weighed and dissolved in 6ml of water. The NaCl solution was added dropwise to the calcined MgO and stirred to ensure good distribution. The resulting mixture was then dried in an oven at 105°C for approximately 16 hours.

[0066] The amorphous Mo-Fe catalyst was sieved to a particle size in the range of 250 μm to 355 μm. The final calcined catalyst composition containing the Fe-Mo catalyst and the MgO impregnated with Na was prepared according to the same method as described in Example 1. The following table shows the amount of reactants used for each sample in this series:

[0067]

[0068] Table 2

[0069] Manual mixing of catalyst components

[0070] Calcined MgO: Commercial MgO (Sigma-Aldrich, 325 mesh) was calcined to 1000°C using a static oven at a ramp rate of 5°C / min and held at the target temperature for 2 hours.

[0071] Na-Impregnated MgO: Prepare a batch of calcined MgO prepared as described above and impregnate it with NaCl to obtain 0.2 wt% Na on the MgO. To do this, dissolve the NaCl in enough desalted water to fill the pores of the MgO without overfilling to allow for even distribution of the NaCl. The amount of solution required per gram of calcined MgO is 0.60 g / ml. In a glass beaker, weigh 9.98 g of calcined MgO. In a separate beaker, weigh 0.05 g of NaCl and dissolve it in 6 ml of water. Add the NaCl solution dropwise to the calcined MgO and stir to ensure good distribution. The resulting mixture is then dried in an oven at 105°C for approximately 16 hours.

[0072] Mo-Fe catalyst: The batch was sieved to a particle size ranging from 250 μm to 355 μm.

[0073] 2i-1 wt% MgO, manually mixed :

[0074] Mo-Fe catalyst (14.85 g) was weighed into a glass beaker, and calcined MgO (0.15 g) was added. The reaction mixture was then carefully stirred with a metal spatula during approximately 5 minutes.

[0075] The samples were then calcined at 400°C to 550°C to obtain the final catalyst composition.

[0076] 2j-1 wt% Na-containing MgO, manually mixed

[0077] Mo-Fe catalyst (14.85 g) was weighed into a glass beaker and calcined Na-impregnated MgO (0.15 g) was added. The reaction mixture was then carefully stirred with a metal spatula during approximately 5 minutes.

[0078] The sample was then calcined at 400°C to 550°C to obtain the final catalyst composition.

[0079] The methyl formate selectivity % and methanol conversion % were evaluated for 2a-j and reference C1.

[0080] The evaluations were conducted in a microreactor at 330°C, 0.5 barg, and a total gas flow rate of 400 Nml / min; the concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0 vol%, 1.4 vol%, 0.2 vol%, 0.26 vol%, 4.06 vol%, 10.0 vol%, and 77.08 vol%, respectively. In separate experiments, the weights of the C1 catalyst used in the microreactor were 0.1 g, 0.15 g, 0.2 g, and 0.25 g, which give the values ​​of Figure 2 The weight of catalysts 2a-j used in the microreactor tests was 0.2 g. Figure 2 The results show that for 0.2 g of catalyst, methyl formate selectivity decreased without a significant decrease in methanol conversion. It is speculated that this effect would also be seen at higher catalyst loadings and methanol conversions. It can also be seen that the catalyst preparation is universal, as both RAM and manual mixing provided catalysts that exhibited similar decreases in methyl formate selectivity. The Na-containing catalyst exhibited decreased catalyst activity, but it is speculated that methyl formate selectivity decreased even more at a given methanol conversion.

[0081] Example 3

[0082] The catalyst composition was prepared according to the procedure described in Example 2. However, the Mo-Fe catalyst was calcined at 400-550°C before blending or mixing with MgO or Na-impregnated MgO, and the final catalyst was not calcined. A catalyst material having the following composition was prepared.

[0083]

[0084] The methyl formate selectivity % and methanol conversion % were evaluated for 3a-1 and reference C1.

[0085] The evaluations were conducted in a microreactor at 330°C, 0.5 barg, and a total gas flow rate of 400 Nml / min; the concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0 vol%, 1.4 vol%, 0.2 vol%, 0.26 vol%, 4.06 vol%, 10.0 vol%, and 77.08 vol%, respectively. In separate experiments, the weights of the C1 catalyst used in the microreactor were 0.1 g, 0.15 g, 0.2 g, and 0.25 g, which give the values ​​of Figure 3 The weight of catalyst 3a-1 used in the microreactor test was 0.2 g. Figure 3The results show that for 0.2 g of catalyst, methyl formate selectivity decreased without a significant decrease in methanol conversion. It is speculated that this effect would also be seen at higher catalyst loadings and methanol conversions. It can also be seen that the preparation of the catalyst composition is universal, as both RAM and manual mixing provided catalysts that exhibited similar decreases in methyl formate selectivity. Similarly, the catalyst containing Na showed decreased catalyst activity, but it is speculated that methyl formate selectivity decreased even more at a given methanol conversion.

[0086] Example 4

[0087] 4a-3 wt% ZrO2 catalyst

[0088] Commercially available ZrO2 (Alpha Aesar) was sieved to a particle size below 53 μm and then calcined to 1000°C using a static oven at a ramp rate of 5°C / min and held at the target temperature for 2 hours.

[0089] The amorphous Mo-Fe catalyst was sieved to a particle size ranging from 250 μm to 355 μm.

[0090] Amorphous Mo-Fe catalyst (14.7 g) was added to a reaction vessel and calcined ZrO (0.3 g) was added. The reaction vessel was then subjected to RAM using a LabRAM II instrument under a force of 80 g for 5 minutes. The sample was subsequently calcined to obtain the final catalyst composition.

[0091] 4b-3 wt% ZrO2:CeO2 (50:50) catalyst

[0092] A commercially available mixture of CeO2:ZrO2 50:50 (Rhodia) was sieved to a particle size below 53 μm and then calcined to 1000°C using a static oven at a ramp rate of 5°C / min and held at the target temperature for 2 hours.

[0093] The amorphous Mo-Fe catalyst was sieved to a particle size ranging from 250 μm to 355 μm.

[0094] Amorphous Mo-Fe catalyst (14.7 g) was added to a reaction vessel and calcined CeO 2 :ZrO 2 50:50 (0.3 g) was added. The reaction vessel was then subjected to RAM using a LabRAM II instrument at a force of 80 g for 5 minutes. The sample was subsequently calcined to obtain the final catalyst.

[0095] The methyl formate selectivity % and methanol conversion % were evaluated for 4a and b and reference C1.

[0096] The evaluations were conducted in a microreactor at 330°C, 0.5 barg, and a total gas flow rate of 400 Nml / min; the concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0 vol%, 1.4 vol%, 0.2 vol%, 0.26 vol%, 4.06 vol%, 10.0 vol%, and 77.08 vol%, respectively. In separate experiments, the weights of the C1 catalyst used in the microreactor were 0.1 g, 0.15 g, 0.2 g, and 0.25 g, which give the values ​​of Figure 4 The weight of catalysts 4a and b used in the microreactor tests was 0.2 g. Figure 4 It is shown that for 0.2 g of catalyst, methyl formate selectivity decreases while methanol conversion increases. It can be speculated that this effect will also be seen at higher catalyst loadings and methanol conversions.

[0097] Example 5

[0098] A catalyst containing 3 wt% MgO was prepared according to the same method as described in Example 1. Before calcination, the catalyst composition was tableted to obtain annular catalyst tablets 5a. For tableting, a compaction simulator was used to prepare single-layer pellets and the mold filling was carried out by a vibrating feeder. After calcination, the tablets had an outer diameter of 5.1 mm and an inner diameter of 2.75 mm. Conventional lubricants and pore formers were used. The reference catalyst C1 was also tableted and calcined to obtain tablets with an outer diameter of 5.0 mm and an inner diameter of 2.75 mm. The average mass and volume of 10 tablets each were used to calculate the density of the calcined tablets at room temperature and ambient pressure. A microscope (Infinity 2 model) was used to measure the thickness of the tablet wall. The tablet outer diameter, height and hardness in the axial direction were tested using a Soakx hardness tester MT50-FT, Standard, TDH, 800N, 100-240V / 50-60Hz. As Figure 5 As can be seen in the graph, tablets containing the catalyst composition according to the present invention are less dense, which is beneficial for catalyst activity, but have a higher hardness. The ability to achieve such a hardness-to-density ratio means, for example, that tablets with a specific hardness that can correspond to the hardness of conventional catalyst pellets can be prepared at a lower density. This has significant benefits for the durability and stability of the catalyst pellets.

[0099] Example 6

[0100] Figure 6TEM images (shown in color and grayscale) of coated particles from a catalyst composition of the present invention comprising 1 wt.% MgO, prepared by the method described above for Sample 1b. As can be seen from the image, a uniform coating of Mg is present on the surface of the particles of the Fe-Mo catalyst material. The surface coating is evident due to the higher Mg density at the edges of the particles in the image and the fact that the blending method used to prepare the catalyst does not result in Mg impregnation into the particles.

[0101] Figure 7 is a collection of EDS images (shown in color and grayscale) of coated particles containing 1 wt% of a catalyst composition of the present invention, prepared by the method described above for Sample 1b. Figure 5 Likewise, from the images it can be seen that there is a uniform Mg coating on the surface of the particles of the Fe-Mo catalyst material. It is also obvious that Fe, O and Mo are present throughout the particles.

[0102] For TEM and EDS measurements, the sample was ground between two glass slides and cast onto a holey carbon-coated CuTEM grid. The sample was examined in a JEM 2800 (scanning) transmission electron microscope using the following instrumental conditions: voltage (kV) 200; C2 apertures (µm) 70 and 40 µm. Darkfield (Z-contrast) imaging was performed in scanning mode using an off-axis annular detector. SE signals were acquired simultaneously with other TEM images that provide topological information about the sample.

Claims

1. A catalyst composition comprising: i) a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and ii) Metal oxide A, wherein the metal oxide A is an alkaline earth metal oxide, or zirconium oxide, or a combination of zirconium oxide and cerium oxide. 2 . The catalyst composition according to claim 1 , wherein the metal oxide A is an alkaline earth metal oxide. The catalyst composition according to claim 2 , wherein the metal oxide A is magnesium oxide. The catalyst composition according to claim 1 , wherein the metal oxide A is zirconium oxide, or a combination of zirconium oxide and cerium oxide.

5. A catalyst composition according to any preceding claim, wherein the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is in particulate form.

6. The catalyst composition according to any preceding claim, comprising a physical blend of the catalytic material and the metal oxide A, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

7. The catalyst composition of claim 5 or claim 6, wherein at least some of the metal oxide A forms a coating around the particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

8. The catalyst composition according to any one of claims 5 to 7, comprising: i) particles of said catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and ii) the metal oxide A; wherein the catalyst composition comprises a physical blend of the catalytic material and the metal oxide A, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); and wherein at least some of the metal oxide A forms a coating around the particles of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

9. The catalyst composition of any preceding claim, wherein the metal oxide A is present in an amount of no more than about 15 wt. %, based on the total weight of the catalyst composition.

10. The catalyst composition of any preceding claim, further comprising an alkali metal.

11. The catalyst composition according to any preceding claim, wherein the metal oxide A is impregnated with the alkali metal.

12. The catalyst composition of claim 10 or claim 11, wherein the alkali metal is present in an amount of no more than about 5 wt% based on the weight of the metal oxide A.

13. A pellet comprising a catalyst composition according to any preceding claim.

14. The pellet of claim 13 having a hardness to density ratio greater than about 9.

15. A method for preparing the catalyst composition according to any one of claims 1 to 12, comprising the steps of: i) calcining metal oxide A to provide calcined metal oxide A; ii) mixing the calcined metal oxide A with a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); iii) calcining the mixture to provide the catalyst composition.

16. A process for preparing a catalyst composition as defined in any one of claims 10 to 12 according to claim 15, comprising the steps of: ii) prior to calcining the metal oxide A, impregnating the metal oxide A with the alkali metal using a salt of the alkali metal to provide an impregnated metal oxide A.

17. A method for producing formaldehyde from methanol, the method comprising the steps of: A feed stream comprising the methanol and an oxygen-containing gas is fed to a reactor; and the methanol in gas phase is reacted with the oxygen-containing gas in the reactor in the presence of the catalyst composition according to any one of claims 1 to 12 or the pellets according to claim 13 or claim 14.

18. The process according to claim 17, wherein the reactor comprises at least one reaction tube, each tube comprising one or more catalyst beds, wherein the one or more catalyst beds in the lower part of the tube comprise the catalyst composition according to any one of claims 1 to 12 or the pellets according to claim 13 or claim 14.

19. Use of a catalyst composition as defined in any one of claims 1 to 13 or a pellet as defined in claim 13 or claim 14 for reducing methyl formate losses in a process for producing formaldehyde from methanol.

20. The use according to claim 19, wherein the method comprises the following steps: feeding a feed stream comprising the methanol and an oxygen-containing gas to a reactor; reacting the oxygen-containing gas with the methanol in a gas phase in the reactor in the presence of the catalyst composition; and recovering a formaldehyde reactor outlet stream from the reactor, the formaldehyde reactor outlet stream comprising formaldehyde and methyl formate.

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